U.S. patent application number 12/942689 was filed with the patent office on 2011-03-03 for range measurement device.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to Michael R. Elgersma, Randolph G. Hartman.
Application Number | 20110051120 12/942689 |
Document ID | / |
Family ID | 40011653 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110051120 |
Kind Code |
A1 |
Hartman; Randolph G. ; et
al. |
March 3, 2011 |
RANGE MEASUREMENT DEVICE
Abstract
A range measurement device is disclosed. The device comprises a
flash laser radar configured to produce a first laser pulse at a
first time. The device receives, at a second time, reflections of
the first laser pulse from at least one object within a 360 degree
field of view. The device further comprises a timing electronics
module, an image sensor in communication with the timing
electronics module, a mirror element coupled between the image
sensor and the laser radar, and a lens. The mirror element includes
a first reflector configured to disperse the reflections of the
first laser pulse within at least a portion of the 360 degree field
of view and a second reflector configured to collect returning
reflections of the first laser pulse from the at least one object
into the image sensor. The lens is configured to focus the
returning reflections onto the image sensor.
Inventors: |
Hartman; Randolph G.;
(Plymouth, MN) ; Elgersma; Michael R.; (Plymouth,
MN) |
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
40011653 |
Appl. No.: |
12/942689 |
Filed: |
November 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11837868 |
Aug 13, 2007 |
7852463 |
|
|
12942689 |
|
|
|
|
Current U.S.
Class: |
356/5.01 |
Current CPC
Class: |
G01S 7/4814 20130101;
G01S 7/4808 20130101; G01S 17/894 20200101; G01S 17/10 20130101;
G01S 17/66 20130101; G01S 17/42 20130101; G01S 7/4816 20130101;
G01S 17/87 20130101; G01S 17/86 20200101 |
Class at
Publication: |
356/5.01 |
International
Class: |
G01C 3/08 20060101
G01C003/08 |
Claims
1. A navigation system, comprising: a range measurement device
operable to provide at least one of angles, ranges, and attitude
data of at least one object, the range measurement device
including: a flash laser radar operable to produce a first laser
pulse at a first time, wherein the range measurement device is
configured to receive, at a second time, reflections of the first
laser pulse from the at least one object within a 360 degree field
of view of the range measurement device; and a processor in
communication with the range measurement device, the processor
configured to: track a range and an attitude based on an output of
the range measurement device to the at least one object within a
localized time period between the first and second times based on
the reflections received from the at least one object; and as
additional reflections are received from the at least one object,
record additional time periods to determine at least one of a
current position and a current attitude of the range measurement
device relative to the at least one object.
2. The system of claim 1, further comprising at least one of an
inertial sensor, a heading sensor, a speed sensor, a global
positioning sensor, and an altimeter sensor in communication with
the processor.
3. The system of claim 1, wherein the processor further comprises
program instructions to determine at least one of an absolute
position and an absolute attitude of the system based on the
measurements to the at least one object with prior information
including at least one known attitude and position.
4. The system of claim 1, wherein the processor further comprises
program instructions to determine at least one of a range
measurement to the at least one object, an azimuth measurement to
the at least one object, and a location measurement of the at least
one object.
5. A method for measuring range to determine position, the method
comprising: producing a first laser pulse with a laser radar at a
first time dispersed over a 360 degree field of view; receiving
reflections of the first laser pulse from at least one object
within the 360 degree field of view at a second time; based on the
returning reflections received at the second time, tracking at
least one of a range and an attitude from a host vehicle having the
laser radar to the at least one object within a localized time
period between the first and second times; and as additional laser
pulse reflections are received, recording additional localized time
periods to determine at least one of a current position and a
current attitude of the host vehicle relative to the at least one
object.
6. The method of claim 5, further comprising determining at least
one of an absolute position and an absolute attitude of the host
vehicle based on the reflections received and a known location of
the at least one object.
7. The method of claim 5, further comprising: synchronizing a range
image of the at least one reflection of the flash laser pulse with
the laser radar at the second time; and determining a relative
velocity between the range measurement device and the at least one
object based on a localized time period between the first and
second times.
8. The method of claim 7, wherein synchronizing the range image of
the reflected tracking signal with the laser radar comprises
determining at least one of a range measurement to the at least one
object, an azimuth measurement to the at least one object, and a
location measurement of the at least one object.
9. The method of claim 5, further comprising determining a relative
range between the range measurement device and the at least one
object.
10. The method of claim 5, wherein receiving the reflections
further comprises determining a relative angle between the at least
one object and the host vehicle based on relative transit
times.
11. The method of claim 5, wherein tracking further comprises:
determining at least one of a relative position and relative
attitude of the at least one object within the 360 degree field of
view; and determining at least one of an absolute position and
absolute attitude of the at least one object when the absolute
position of the at least one object is known.
12. The method of claim 5, wherein tracking further comprises:
determining a relative position angle between the at least one
object and the host vehicle, wherein the at least one object is a
targeted object; determining at least a relative position and
relative attitude to the targeted object; and determining at least
one of the absolute position and absolute attitude of the targeted
object when the absolute position of the laser radar is known.
13. The method of claim 5, wherein recording the additional
localized time periods comprises at least one of: measuring the
additional signal reflections to determine a current heading,
pitch, and roll of the host vehicle; and measuring the signal
reflections to determine a location of the target relative to the
host vehicle.
Description
[0001] This application is a divisional application of U.S.
application Ser. No. 11/837,868, filed on Aug. 13, 2007, the
disclosure of which is incorporated herein by reference.
[0002] This application is also related to commonly assigned and
co-pending U.S. application Ser. No. 11/678,313, filed on Feb. 23,
2007, published as US 2008/0208455 A1, the disclosure of which is
incorporated herein by reference.
BACKGROUND
[0003] Many navigation applications provide precise locating and
tracking of objects when necessary. For example, unmanned vehicles,
such as an unmanned ground vehicle (UGV), require accurate position
information in order to properly navigate an area. Most of these
navigation applications employ one or more global positioning
system (GPS) sensors to achieve a necessary level of precision.
[0004] The use of GPS, however, has some limitations. For example,
the GPS signals may not be available in a desired location where
satellite communication is blocked or scrambled. In addition, the
GPS sensors do not obtain any local features of the area (for
example, any additional surrounding objects or landmarks within the
area) relative to the location of the vehicle. To date, tracking
any localized features requires additional synchronization time in
instances where accurate measurements within a minimal time period
are critical.
[0005] For the reasons stated above and for other reasons stated
below which will become apparent to those skilled in the art upon
reading and understanding the present specification, there is a
need in the art for improvements in range measurements and object
position tracking.
SUMMARY
[0006] The following specification discusses a range measurement
device. This summary is made by way of example and not by way of
limitation. It is merely provided to aid the reader in
understanding some aspects of at least one embodiment described in
the following specification.
[0007] Particularly, in one embodiment, a range measurement device
is provided. The device comprises a flash laser radar configured to
produce a first laser pulse at a first time. The device receives,
at a second time, reflections of the first laser pulse from at
least one object within a 360 degree field of view. The device
further comprises a timing electronics module, an image sensor in
communication with the timing electronics module, a mirror element
coupled between the image sensor and the laser radar, and a lens.
The mirror element includes a first reflector configured to
disperse the reflections of the first laser pulse within at least a
portion of the 360 degree field of view and a second reflector
configured to collect returning reflections of the first laser
pulse from the at least one object into the image sensor. The lens
is configured to focus the returning reflections onto the image
sensor.
DRAWINGS
[0008] These and other features, aspects, and advantages are better
understood with regard to the following description, appended
claims, and accompanying drawings where:
[0009] FIG. 1 is a block diagram of a navigation system;
[0010] FIG. 2 is a traverse diagram of a vehicle having the system
of FIG. 1 traversing through an area;
[0011] FIG. 3 is a block diagram of a range measurement device;
[0012] FIG. 4 is a flow diagram of a method for measuring range;
and
[0013] FIG. 5 is a flow diagram of an alternate method for
measuring range.
[0014] The various described features are drawn to emphasize
features relevant to the teachings of the present application. Like
reference characters denote like elements throughout the figures
and text of the specification.
DETAILED DESCRIPTION
[0015] Embodiments of the present invention relate to a range
measurement device that determines an absolute location and
attitude of the system with respect to local objects with absolute
known locations (referred to herein as targeted objects) and, in at
least one alternate application, a relative location and attitude
of the system with respect to any local objects within range of the
range measurement device (referred to herein as surrounding
objects). In one embodiment, the range measurement device discussed
herein determines the location of the system using a pulse from a
laser radar (LADAR). Moreover, the range measurement device
provides synchronized measurements of the surrounding objects
within a 360.degree. field of view along the horizon and returns
the distance and angular relationship between the range measurement
device and the surrounding objects. With these distance and angular
relationships, a location and attitude of the system is determined
within a localized area with respect to the surrounding objects. In
one implementation, the range measurement device mounts on an
unmanned ground vehicle (UGV) interested in at least one of
recording an absolute location of the UGV, tracking another vehicle
or object within the localized area, and determining a relative
location and attitude of the UGV within the localized area.
[0016] The use of a LADAR improves range tracking accuracy. The
range measurement device discussed here measures an accurate range
as well as the angular relationship of the surrounding objects
relative to the range measurement device. In one implementation,
range, location, and azimuth measurements of the surrounding
objects are synchronously measured to a plurality of
three-dimensional (3-D) images using the LADAR output. The accurate
range measurements are used to locate the device either absolutely
or relatively (which is useful in 3-D rendering and mapping
applications and allows for localization and mapping in a single
process).
[0017] In one implementation, the LADAR produces a laser pulse and
a charge-coupled device (CCD) sensitive to the laser pulse receives
at least one reflection from the surrounding objects "of interest."
Based on the reflection(s) received, the CCD can measure a flight
time of the laser pulse. In the same and at least one alternate
implementation, measurements from the CCD are used by a processor
in the range measurement device to determine the location of the
UGV relative to any of the surrounding objects identified.
Moreover, given the absolute location of the UGV, location
coordinates (for example, latitude, longitude, and altitude) of the
object are produced. Likewise, the 3-D information can be used to
determine the attitude of the object (for example, heading pitch
and roll).
[0018] FIG. 1 is a block diagram of a navigation system 100. As
illustrated, the navigation system 100 includes a processor 102
that is in communication with a range measurement device 106
(which, in this embodiment, comprises a 360.degree. 3-D flash
LADAR). In some embodiments, the system 100 includes at least one
additional sensor such as a GPS sensor 108, an inertial sensor 110,
a heading sensor 112, a speed sensor 114, and an altimeter sensor
116.
[0019] The range measurement device 106 provides range data,
including distances and angles, to the processor 102 of objects
near a host vehicle having the system 100. Many methods of
communication are possible including CCD pixel information,
however, one skilled in the art can determine methods for providing
distance and angle information. As indicated above, in one
embodiment, a 360.degree. 3-D flash LADAR is used in the range
measurement device 106. The LADAR-based range measurement device
106 detects and locates the objects using a single flash of laser
light and provides information similar to radar. Moreover, the
range measurement device 106 illuminates a 360.degree. field of
view so that objects in any direction along the horizon from the
range measurement device 106 are located (for example, located as
the host vehicle traverses throughout an area, similar to the area
discussed below with respect to FIG. 2). As the host vehicle passes
through the area, the range measurement device 106 tracks
individual angles and ranges between the objects and the range
measurement device 106 (for example, relative distance data). When
absolute position information for the objects is known, the
relative distance data can be transformed to Earth-referenced
angles for the objects in a specified area (for example, relative
distance data). Both the relative and absolute distance data are
processed in the processor 102.
[0020] In the embodiment that includes the inertial sensor 110,
additional information is provided to the processor 102 to estimate
the location of the host vehicle. Generally, the inertial sensor
110 estimates a present position based on a prior knowledge of
time, initial position, initial velocity, initial orientation
without the aid of external information. As illustrated in FIG. 1,
an initial position input and an initial heading input is provided.
The information generated by the inertial sensor 110 (in this
embodiment) is provided to the processor 102. The processor 102
uses the inertial sensor 110 data, in combination with the distance
and angle data, from the ranging device 106 to determine the
current location of the host vehicle. The current location and
current heading is output as illustrated in FIG. 1. The output of
the current heading and current location is used to position the
system 100 with both absolute and relative navigation
coordinates.
[0021] FIG. 2 is a traverse diagram 200 illustrating a host vehicle
207 (for example, a UGV) passing through an area 200 to be
traversed. As illustrated, the area 200 to be traversed includes
objects 210.sub.1 through 210.sub.N. In one implementation, the
objects 210.sub.1 through 210.sub.N are mapped (for example,
previously located) according to a correlation position
determination method as disclosed in the '313 application. In
alternate implementations, locations of the objects 210.sub.1
through 210.sub.N are not previously known. The host vehicle 207
takes a path 206 that starts at a first point 202 and ends at a
second point 204. The host vehicle 207 comprises a navigation
system 208 including the range measurement device 106 of FIG. 1. In
the example embodiment of FIG. 2, the range measurement device 106
of the navigation system 208 transmits (for example, flashes a
laser light pulse from a flash LADAR) and receives a 3-D image of
the objects 210 through the use of a mirror element and an image
sensor, as further described below with respect to FIG. 3.
[0022] FIG. 3 is a block diagram of a range measurement device 300.
In the example embodiment of FIG. 3, the device 300 represents the
range measurement device 106 of FIG. 1. The device 300 in this
embodiment comprises a flash laser radar (LADAR) 302, a mirror
element 304 (comprising a first reflector 314 and a second
reflector 316), and a timing electronics module 306 in
communication with the image sensor 310 and a lens 308. In the
example embodiment of FIG. 3, the timing electronics module 306
monitors sensitivity of the image sensor 310 by controlling a
shutter of the lens 308 with a "Shutter Control Signal"
communication link. Moreover, the timing electronics module 306
controls the initiation of a first laser pulse originating from the
flash LADAR 302 to illuminate a target (for example, the objects
210 of FIG. 2) with a "Flash Control Signal" communication link. In
one implementation, the timing electronics modules 306 further
comprises one or more timers 312 operable to measure signal transit
timing of the first laser pulse with a "Timing Control Signal"
communication link as shown in FIG. 3.
[0023] In the example embodiment of FIG. 3, the image sensor 310 is
a charge-coupled device (CCD). The image sensor 310 consists of an
integrated circuit containing an array of linked, or coupled,
light-sensitive capacitors (that is, pixels). In one
implementation, the mirror element 304 is a 3-D reflective surface.
Moreover, the first reflector 314 is one of a cone, a trapezoid, a
sphere, or any other surface which can disperse the first laser
pulse into the required field, and the second reflector 316 is one
of a cone, a trapezoid, a sphere, or any other surface which can
focus a first reflected laser pulse into the lens 308, as further
discussed below. The image sensor 310 contains at least one pixel
grid array to sense the returned 3-D reflections from the mirror
element 304. As discussed in further detail below, the image sensor
310 further provides the intensity of the reflection to the
processor 102 and terminates the signal transit timing in the
timing electronics module 306.
[0024] In operation, the flash LADAR 302 illuminates the objects
210 surrounding the device 300 in a 360.degree. radius through a
reflective surface (for example, the mirror element 304). In one
implementation, the first reflector 314 is configured to disperse
reflections of a first laser pulse into a 360.degree. field of
view. The second reflector 316 collects returning laser pulse
reflections of the first laser pulse onto the lens 308. In one or
more alternate implementations, at least a portion of the field of
view less than 360.degree. can be selected. For example, the first
laser pulse from the flash LADAR 302 reflects in all directions
(that is, the first laser pulse reflects 360.degree.) from the
first reflector 314 and returns the reflections back from the
objects 210 to the second reflector 316. In turn, the lens 308
focuses the return reflections from the second reflector 316 on a
focal plane of the image sensor 310. From the return reflection(s)
of the second reflector 316, the lens 308 captures an image of at
least one of the objects 210 for the image sensor 310. In the
example embodiment of FIG. 3, the focused reflection captured by
the lens 308 causes each capacitor in the pixel array of the image
sensor 310 to accumulate an electric charge proportional to the
light intensity at the location of each of the objects 210.
[0025] Using the pixel intensity locations from the image sensor
310, relative angular measurements of each of the objects 210 are
taken by the processor 102. A local distance between the flash
LADAR 302 and the surrounding objects 210 is also determined given
a propagation time of the flash LADAR 302 from flash to reception
taken at each pixel of the image sensor 310. A relative range for
each of the objects 210 is computed given the local distance and a
relative velocity (for example, the speed of light) of the first
laser pulse return reflections. The relative range is calculated
based on the length of time it takes for the light (for example,
the first laser pulse) to return from the target.
[0026] Using the relative angular and range information, a 3-D
image is created. In one embodiment, once the lens 308 receives the
reflection image, independent pixels within the image sensor 310
stop the timers 312 of the timing electronics module 306. The image
sensor 310 measures the change in light intensity to stop the
signal transit timing (initiated at the time the "Flash Control
Signal" is sent from the timing electronics module 306 to the flash
LADAR 302) to determine the relative range to each of the objects
210 for each illuminated pixel in the image sensor 310. The
propagation time between initializing the first laser pulse and the
received reflection image is proportional to the range from the
range measurement device 300 to the objects 210 based on the
relative velocity of the first laser pulse return reflections. In
one implementation, range, location, and azimuth measurements of
the objects 210 are synchronized to each 3-D image produced.
[0027] In one implementation, given the relative angles and
distances discussed above, the host vehicle 207 (of FIG. 2) is
localized with as few as two measurements. Moreover, the laser
pulses available with the flash LADAR 302 increase the measurement
accuracy of the range measurement device 300. In one
implementation, any potential objects of interest are localized
relative to the host vehicle 207 with the range measurement device
300 as discussed below.
Localized Navigation Based on LADAR Range Data
[0028] In the example embodiments of FIGS. 2 and 3, accurately
measured ranges are used to locate the host vehicle 207 to at least
four objects 210 previously surveyed. In identifying the at least
four surveyed objects 210 as targeted objects, each pixel on the
image sensor 310 records range to whatever illuminated that pixel.
In one implementation, only pixels with very strong returns are
considered since those pixels will correspond to reflective
surveyed markers present on the at least four surveyed objects 210.
It is understood that many means exist for identifying the targeted
objects 210 that are well known in the art. In one implementation,
a first pixel coordinate (i,j) in (for example) a 128.times.128
pixel layer CCD in the image sensor 310 provides an estimate of a
unit-vector towards at least one of the objects 210 that
illuminated the first pixel at (i, j). Together, the range and unit
vector provide a first estimate of the targeted object 210's
location in polar coordinates. Additionally, this first estimate
identifies which of the at least four (surveyed) objects 210 is
illuminating the first pixel. In the example embodiment of FIG. 2
(given the surveyed ranges of the targeted objects 210), an
accurate estimate of the location of the host vehicle 207 is
determined with Equations 1 to 6 described below, where subtracting
two range equations (for example, Equations 1 and 2) eliminates the
unknown quadratic terms and results in a linear equation (for
example, Equation 3).
[0029] In one implementation, Equations 1 and 2 illustrated below
use Cartesian grid coordinates (x.sub.1,y.sub.1,z.sub.1) and
(x.sub.2,y.sub.2,z.sub.2) for the location of the objects 210.sub.1
and 210.sub.2 at two known locations, and a first unknown position
(x.sub.0,y.sub.0,z.sub.0), with measured ranges of r.sub.1 and
r.sub.2 from the range measurement device 300 to the objects
210.sub.1 and 210.sub.2.
(x.sub.0-x.sub.1).sup.2+(y.sub.0-y.sub.1).sup.2+(z.sub.0-z.sub.1).sup.2--
r.sub.1.sup.2=0 Equation 1
(x.sub.0-x.sub.2).sup.2+(y.sub.0-y.sub.2).sup.2+(z.sub.0-z.sub.2).sup.2--
r.sub.2.sup.2=0 Equation 2
[0030] As illustrated above, the only unknown quadratic terms in
Equations 1 and 2 are x.sub.0.sup.2+y.sub.0.sup.2+z.sub.0.sup.2. By
subtracting Equations 1 and 2, all the unknown quadratic terms
cancel (for example, Equation 1-Equation 2=0) as illustrated below
in Equation 3.
2*((x.sub.2,y.sub.2,z.sub.2)-(x.sub.1,y.sub.1,z.sub.1))'*(x.sub.0,y.sub.-
0,z.sub.0)+r.sub.2.sup.2-r.sub.1.sup.2+.parallel.(x.sub.1,y.sub.1,z.sub.1)-
.parallel..sup.2-.parallel.(x.sub.2,y.sub.2,z.sub.2).parallel..sup.2=0
Equation 3
[0031] Equation 3 as discussed above is a linear equation with
unknowns (x.sub.0,y.sub.0,z.sub.0). The symbol .parallel.
.parallel..sup.2 is defined as illustrated below in Equation 4.
.parallel.(x.sub.n,y.sub.n,z.sub.n).parallel..sup.2=x.sub.n.sup.2+y.sub.-
n.sup.2+z.sub.n.sup.2 where n=1, 2, . . . Equation 4
[0032] In the example embodiment of FIG. 2, the at least four
surveyed markers (that is, the objects 210.sub.1 to 210.sub.4)
result in at least six linear equations from the six combinations
(for example, (1-2), (1-3), (1-4), (2-3), (2-4) and (3-4)) as shown
below:
(Equation 1)-(Equation 2)=0
(Equation 1)-(Equation 3)=0
(Equation 1)-(Equation 4)=0
(Equation 2)-(Equation 3)=0
(Equation 2)-(Equation 4)=0
(Equation 3)-(Equation 4)=0
[0033] The above example provides at least 6 linear equations with
at least 3 unknowns (x.sub.0,y.sub.0,z.sub.0), which are solved
using commonly-known linear algebra and a least squares solution.
These equations are written in vector notation as illustrated below
in Equation 5, with a least squares solution to [{circumflex over
(x)}] shown below in Equation 6.
[A][x]=[b] Equation 5
[{circumflex over (x)}]=[A.sup.TA].sup.-1[A.sup.T][b] Equation
6
[0034] The result of Equation 6 is a location of the host vehicle
207, [{circumflex over (x)}], localized to the targeted objects 210
using the range data of the flash LADAR 302.
[0035] FIG. 4 is a flow diagram of a method 400 for measuring range
to determine a laser radar position. For example, the method 400
uses a range measurement device similar to the range measurement
device 300 of FIG. 3 to perform 360.degree. range tracking of an
area surrounding a vehicle (for example, the host vehicle 207 of
FIG. 2). The method discussed here returns the distance and angular
relationship between the vehicle and any surrounding objects
currently positioned in the area. For example, the range
measurement device 300 includes a flash, a mirror element, and a
CCD-based image sensor so that the surrounding objects can be
detected in a 360.degree. field of view.
[0036] At block 402, the range measurement device produces a first
laser pulse with the laser radar at a first time dispersed over the
360.degree. field of view. In one implementation, a timing
electronics module of the range measurement device controls the
initiation of the first laser pulse in order to properly illuminate
at least one surrounding object. The range measurement device
receives reflections of the first laser pulse reflected from
surrounding objects within the 360 degree field of view at a second
time (block 404). In one implementation, the second time comprises
a relative transit time of the reflected first laser pulse within a
localized time period between the first and second times. Based on
the reflections received, the range measurement device tracks at
least one of a range and an attitude from the vehicle to the at
least one surrounding object (block 406). In one implementation,
signal transit times between producing the flash pulse to reception
at the CCD-based image sensor and pixel intensity locations
measured by the CCD-based image sensor are used to determine the
relative angles and relative ranges of the surrounding objects.
[0037] As additional reflections are received, the range
measurement device determines additional localized time periods to
determine at least one of a current position and a current attitude
of the host vehicle relative to the surrounding objects (block
408). In one implementation, computing performed at block 408
comprises measuring the additional localized time periods to
determine a current heading, pitch, and roll of the vehicle. In
addition, based on the reflections received and a known absolute
position of the targeted objects, the range measurement device
determines an absolute position of the vehicle, records at least
one relative position angle between the target and the vehicle, and
computes at least one of an absolute position and absolute attitude
to the targeted objects (block 410).
[0038] FIG. 5 is a flow diagram of a method 500 for measuring range
to determine target positions. For example, the method 500
addresses using a first laser pulse from the range measurement
device 300 of FIG. 3 to perform 360.degree. range tracking of an
area surrounding a vehicle (for example, the host vehicle 207 of
FIG. 2) and returns the distance and angular relationship between
the vehicle and any (known) targeted objects currently positioned
in the area. The range measurement device used for the method of
FIG. 5 includes a flash, a mirror element, and a CCD-based image
sensor for the targeted objects of the objects 210 to be detected
in a 360.degree. field of view.
[0039] At block 502, the range measurement device produces a first
laser pulse with the laser radar at a first time dispersed over the
360.degree. field of view. In one implementation, a timing
electronics module of the range measurement device controls the
initiation of the first laser pulse in order to properly illuminate
at least one surrounding object. The range measurement device
receives reflections of the first laser pulse from surrounding
objects within the 360 degree field of view at a second time (block
504). In one implementation, the second time comprises a relative
transit time of the reflected first laser pulse within a localized
time period between the first and second times. Based on the
reflections received, the range measurement device tracks at least
one of a range and an attitude from the vehicle to the at least one
surrounding object (block 506). In one implementation, signal
transit times between producing the flash pulse to reception at the
CCD-based image sensor and pixel intensity locations measured by
the CCD-based image sensor are used to determine the relative
angles and relative ranges of the targeted objects. As additional
reflections are received, the range measurement device determines
additional localized time periods to determine at least one of a
relative position and relative attitude to the targeted objects
(block 508). In addition, based on a known absolute position of the
laser radar, the range measurement device computes at least one of
an absolute position and absolute attitude to the targeted objects
at block 510.
[0040] While the embodiments disclosed have been described in the
context of a navigational system, apparatus embodying these
techniques are capable of being distributed in the form of a
machine-readable medium of instructions and a variety of program
products that apply equally regardless of the particular type of
signal bearing media actually used to carry out the distribution.
Examples of machine-readable media include recordable-type media,
such as a portable memory device; a hard disk drive (HDD); a
random-access memory (RAM); a read-only memory (ROM);
transmission-type media, such as digital and analog communications
links; and wired (wireless) communications links using transmission
forms, such as (for example) radio-frequency (RF) and light wave
transmissions. The variety of program products may take the form of
coded formats that are decoded for actual use in a particular
navigational system incorporating the range measurement device
discussed here by a combination of digital electronic circuitry and
software (or firmware) residing in a programmable processor (for
example, a special-purpose processor or a general-purpose processor
in a computer). At least one embodiment can be implemented by
computer-executable instructions, such as program product modules,
using the programmable processor. The computer-executable
instructions, any associated data structures, and the program
product modules represent examples of executing the teachings of
the present application disclosed herein.
[0041] This description has been presented for purposes of
illustration, and is not intended to be exhaustive or limited to
the embodiments disclosed. Variations and modifications may occur,
which fall within the scope of the following claims.
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